Mobile personal computers are continuing to be thinner, smaller, and lighter. However, the memory capacity required by these mobile personal computers is expanding rapidly, necessitating the use of large-capacity external storage device. Optical recording media such as CD-R/RWs and DVDs are used as external memory for mobile personal computers since they feature large capacity and are easy to operate.
Accordingly, disk drives are widely used as external storage devices. A conventional disk drive is described next with reference to drawings. FIG. 8 is a perspective of a conventional disk drive, and FIG. 9 is a perspective of a pickup module in FIG. 8. FIG. 10 is a perspective of a pickup in FIG. 9, and FIG. 11 is a structural sectional view of a flexible printed circuit sheet (FPC) used in FIG. 10.
As shown in FIG. 8, the disk drive is configured by assembling pickup module 111 (hereafter referred to as PUM) onto tray 112, and covering this tray 112 with housing 113. Pickup module 111, as shown in FIG. 9, is made by assembling spindle motor 115 and pickup 116 on base 114.
Pickup 116, as shown in FIG. 10, has an optical element consisting of carriage unit 123, actuator 125, and object lens 126; FPC unit 122; and hologram unit 127. Actuator 125 supports object lens 126 such that object lens 126 can be slightly displaced in the focus direction and tracking direction during driving. Actuator FPC 8 supplies power for driving actuator 125 that effects this displacement.
Hologram unit 127 has a built-in laser beam source, and emits and converges the laser beam on an optical recording medium through object lens 126. Hologram unit 127 also has a built-in photodetector to detect reflected light from the optical recording medium to reproduce information in the optical recording medium as a signal. FPC unit 122 supplies power to hologram unit 127, and transmits reproducing signals. FPC unit 122 is provided with adjustment slack 132 (where bent through 90°) at the connecting point of FPC unit 122 and hologram unit 127 for adjusting hologram unit 127 by rotating it.
FIG. 11 is a sectional view taken along Line X—X in FIG. 10. FPC unit 122 has a two-layer structure to secure stable electrical characteristics by providing as broad a grounding area (GND) as possible in the electrical circuit configuration. A first layer (LY1) is configured with film 143 on its bottom, followed by adhesive 142, copper foil 141, adhesive 142, and film 143. A second layer (LY2) is configured with adhesive 142, copper foil 141, adhesive 142, and film 143 downward from the bottom face of the first layer in FIG. 11. The copper foil in the first layer and the copper foil in the second layer are connected via a conductive through-hole 148 (hereafter referred to as through-hole). The conventional FPC unit as configured above can only be produced by a limited number of manufacturers. In addition, the FPC unit is extremely expensive due to the need for considerable man-hours and high material costs.
Optical recording and reproducing devices (disk drives) are required to be ever slimmer, smaller, and lighter. In line with the recent sharp drop in OA equipment price, significant cost reductions are also demanded for optical recording and reproducing devices and their components. However, the conventional configuration prevents any significant reduction of FPC cost.